Phosgene → 5-Nitro-1H-benzo[d][1,3]oxazine-2,4-dione

Reaction equation

Cl.[NH2:2][C:3]1[CH:11]=[CH:10][CH:9]=[C:8]([N+:12]([O-:14])=[O:13])[C:4]=1[C:5]([OH:7])=[O:6].[C:15](Cl)(Cl)=[O:16]>O.O1CCCC1>[N+:12]([C:8]1[CH:9]=[CH:10][CH:11]=[C:3]2[NH:2][C:15](=[O:16])[O:7][C:5](=[O:6])[C:4]=12)([O-:14])=[O:13]

Participants

Procedure

A solution of 56.5 g of 2-amino-6-nitrobenzoic acid hydrochloride in 200 ml of demineralized water and 200 ml of tetrahydrofuran is cooled to 10° while stirring and treated with phosgene at 10°-30° for 1 hour, a precipitate resulting. The mixture is subsequently diluted with 300 ml of demineralized water and air is conducted through the suspension vigorously for about 3 hours (until the sample is negative for phosgene). The precipitate is filtered off, washed with water and dried in vacuo over phosphorus pentoxide. There is obtained 6-nitroisatoic acid anhydride as beige crystals of m.p. 220°-222° (decomposition).